To mark World AIDS Day (December 1st), LIFE magazine looks at the story behind the iconic 1990 photograph of David Kirby and his family that put a human face on the AIDS epidemic, and showed the world how it affected families as well as its victims. Photographer Therese Frare shares how it came about.

“Early on,” Frare says of her time at Pater Noster House, “I asked David if he minded me taking pictures, and he said, ‘That’s fine, as long as it’s not for personal profit.’ To this day I don’t take any money for the picture. But David was an activist, and he wanted to get the word out there about how devastating AIDS was to families and communities. Honestly, I think he was a lot more in tune with how important these photos might become.”

Frare pauses, and laughs. “At the time, I was like, Besides, who’s going to see these pictures, anyway?“

Over the past 20 years, by some estimates, as many as one billion people have seen the now-iconic Frare photograph that appeared in LIFE, as it was reproduced in hundreds of newspaper, magazine and TV stories — all over the world — focusing on the photo itself and (increasingly) on the controversies that surrounded it.

Those controversies included the use of the photo in a Benetton ad, which drew the ire of activists and others. But you might not know what else happened after Kirby's death. His parents went through it all again, as they became caregivers to the hospice worker who cared for David, when he also succumbed to AIDS. Frare documented his story in pictures as well, which you can see in the article at LIFE. -via Digg